Rigidity of three-dimensional lattices and dimension reduction in heterogeneous nanowires

In the context of nanowire heterostructures we perform a discrete to continuum limit of the corresponding free energy by means of Γ-convergence techniques. Nearest neighbours are identified by employing the notions of Voronoi diagrams and Delaunay triangulations. The scaling of the nanowire is done in such a way that we perform not only a continuum limit but a dimension reduction simultaneously. The main part of the proof is a discrete geometric rigidity result that we announced in an earlier work and show here in detail for a variety of three-dimensional lattices. We perform the passage from discrete to continuum twice: once for a system that compensates a lattice mismatch between two parts of the heterogeneous nanowire without defects and once for a system that creates dislocations. It turns out that we can verify the experimentally observed fact that the nanowires show dislocations when the radius of the specimen is large

Lagrangian and Eulerian Descriptions in Solid Mechanics and Their Numerical Solutions in hpk Framework

In this thesis mathematical models for a deforming solid medium are derived using conservation laws in Lagrangian as well as Eulerian descriptions. First, most general forms of the mathematical models permitting compressibility of the matter are considered which are then specialized for incompressible medium. Development of constitutive equations central to the validity of the mathematical models is considered Numerical solution of these mathematical models are obtained using finite element method based on h,p,k mathematical and computational framework in which the integral forms are variationally consistent and hence the resulting computational processes are unconditionally stable. Details of the constitutive equations in both Lagrangian and Eulerian descriptions are presented. A variety of model problems are chosen for numerical studies. The wave propagation model problems are considered for numerical studies to investiage (i) Behaviors and limitations of constitutive models in both descriptions (ii) Overall benefits and drawbacks of Lagrangian and Eulerian descriptions

Recent mathematical developments in the Skyrme model

In this review we present a pedagogical introduction to recent, more mathematical developments in the Skyrme model. Our aim is to render these advances accessible to mainstream nuclear and particle physicists. We start with the static sector and elaborate on geometrical aspects of the definition of the model. Then we review the instanton method which yields an analytical approximation to the minimum energy configuration in any sector of fixed baryon number, as well as an approximation to the surfaces which join together all the low energy critical points. We present some explicit results for B=2. We then describe the work done on the multibaryon minima using rational maps, on the topology of the configuration space and the possible implications of Morse theory. Next we turn to recent work on the dynamics of Skyrmions. We focus exclusively on the low energy interaction, specifically the gradient flow method put forward by Manton. We illustrate the method with some expository toy models. We end this review with a presentation of our own work on the semi-classical quantization of nucleon states and low energy nucleon-nucleon scattering.Comment: 129 pages, about 30 figures, original manuscript of published Physics Report